Development of Rapid Cell Recovery System Using Temperature-Responsive Nanofiber Surfaces

Abstract:

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PHBV ultrafine fibers were fabricated by electrospinning process. Electrospun PHBV
fiber structures revealed randomly aligned fibers with average diameter of 400 nm. PIPAAm was
grafted on the surface of PHBV nanofibrous mat by electron beam irradiation. PIPAAm-grafted
PHBV mats were determined by ATR-FTIR and ESCA. Water contact angles were determined by a
sessile drop method at 20 and 37. To examine the tissue compatibility, human fibroblasts were
evenly seeded onto PIPAAm-grafted PHBV mat and cast film, ungrafted PHBV mat and film.
Attached and spread fibroblasts on nanofibrous mat were proliferated more rapidly than that of flat
film surface. Initial cell attachment on PIPAAm-grafted surfaces was higher than ungrafted
surfaces. The surface property changed to hydrophilic by PIPAAm graft, which increased initial cell
attachment. Detachment of single cells from PIPAAm-grafted PHBV matrixes was measured by
low temperature treatment after incubation at 37. Cultured cells were rapidly detached from
PIPAAm-grafted PHBV mat compared with film. With porous mats, the water molecules easily
reach to grafted PIPAAm from underneath and peripheral to the attached cells, resulting in rapid
hydration of grafted PIPAAm molecules and detachment of the cells.

Abstract: The adhesion of bone cells on substrate materials is generally measured by the removal
torque and/or contact area between bone and implants. In this study, collagen was used as a surfacegrafting
material on hydroxyapatite (HA) substrates to enhance the cell adhesion because the
collagen is a major constituent of connective tissues and has been regarded as one of the most
excellent coating materials for bone bonding. First, HA disks (10mmΦ x 1mm) were prepared and
then collagen was immobilbized on the HA surface using an 3-APTES coupling agent to improve
the adhesiveness of cells on HA disk surfaces. NIH 3T3 fibroblasts were seeded on the collagengrafted
and non-grated HA disks and cultured in a Dulbecco’s modified eagle medium containing
10% fetal bovine serum for 3 hrs to evaluate the cell adhesion on the HA samples. The fibroblasts
on the collagen-grafted sample were more spread than those on the non-grafted sample. It is
believed that collagen-grafted HA surface provides suitable sites for cell attaching due to the high
biocompatibility of collagen.

Abstract: Rapid recovery of cell sheets is considered important to maintain the biological function
and viability of recovered cell sheets. To accelerate required culture substrate hydrophilic/
hydrophobic structural changes in response to culture temperature alteration, poly(2-hydroxyethyl
methacrylate) (PHEMA) and poly(N-isopropylacrylamide) (PIPAAm) were grafted successively
onto tissue culture polystyrene (TCPS) dishes by electron beam irradiation. Analysis by attenuated
total reflection-Fourier transform infrared revealed that PHEMA and PIPAAm were successfully
grafted to surfaces of TCPS dish. PIPAAm-PHEMA-grafted TCPS (PIPAAm-PHEMA-TCPS)
dishes were compared with PIPAAm-grafted TCPS dishes for cell sheet detachment experiments.
Approximately 75 min was required to completely detach cell sheets from PIPAAm-TCPS dish,
compared to only 13 min to detach cell sheets from PIPAAm-PHEMA-TCPS dish, which is
successively grafted with PHEMA and PIPAAm. PHEMA is a well-known as a high hygroscopic
polymer. In the case of PIPAAm-PHEMA-TCPS dish, PHEMA layer acted as a water pool to
accelerate the hydration of PIPAAm layer due to the effective and simultaneous water supply to
PIPAAm layer, resulting in rapid hydration of grafted PIPAAm molecules and detachment of cell
sheet compare to PIPAAm-TCPS dish without PHEMA layer.

Abstract: A collagen material was chemically grafted on hydroxyapatite (HA) to enhance bone cell attachment because the collagen is a major constituent of connective tissues and has been regarded as one of the most excellent coating materials for bone bonding. First, HA disks were prepared with 12mm diameter and 1mm thickness. And then collagen (type I) was immobilbized on the HA surface using a 3-APTES coupling agent on HA disk surfaces. MC3T3-E1 osteoblasts were seeded on the collagen-grafted and non-grated HA disks and cultured for 4 hrs to evaluate the cell adhesion on the HA discs. The Attached cell morphology on discs was observed with a fluorescent optical microscopy (FOM) and a scanning electron microscopy (SEM). The osteoblasts on the collagen-grafted sample were more spread than those on the non-grafted sample. It is believed that collagen-grafted HA surface provides suitable sites for cell attaching due to the high biocompatibility of collagen.

Abstract: In order to improve the water flux of PVDF hollow-fiber membrane, acrylic acid (AA) was grafted onto PVDF membrane matrix through electron beam irradiation in isopropanol/water aqueous solution. The grafting conditions were optimized and the effects of grafting parameters were investigated. Fourier transform infrared attenuated total reflection spectroscopy (FTIR-ATR) was used to characterize the chemical changes of the PVDF matrix. The morphological behaviors have been estimated using field emitting scanning electron microscopy (FESEM). The present study suggested that the grafting degree played a dominant role in the water flux of AA grafted PVDF membrane (PVDF-g-AA). The pure water flux of grafted membrane increased to 467.8 L/m2h, nearly two times than the original membrane.